EVOH resin is transparent and excellent in gas-barrier property, odor retention, solvent resistance, and oil resistance. Therefore EVOH resin is formed to film, sheet or a container such as bottle and cup, which is used as a packaging for food, pharmaceutical, industrial medicine, agricultural chemicals, and so on. EVOH resin can be solely applied to packaging such as sheet, film and container, however, EVOH resin is commonly laminated with a layer of a thermoplastic resin other than EVOH resin through an adhesive resin layer to form to a multilayered sheet or film for ensuring water resistance, improved strength, and other functional properties.
Since EVOH resin is less stretched than other thermoplastic resin, EVOH resin is required to improve stretchability in order to follow up the other thermoplastic resin in hot-drawing for forming to an article such as film, sheet, and container.
In general, the higher content of ethylene unit an EVOH resin has, the higher stretchability the EVOH resin tends to exhibit. On the other hand, the higher content of ethylene unit an EVOH resin has, the lower content of vinyl alcohol structural unit the EVOH resin has, the lower the gas-barrier property is. Hereinafter, the content of ethylene unit and the content of vinyl alcohol structural unit are simply called “ethylene content” and “vinyl alcohol content” respectively. In order to obtain both excellent gas-barrier property and stretchability, use of an EVOH resin having high vinyl alcohol content (i.e. low ethylene content and high saponification degree) together with an EVOH resin having low vinyl alcohol content (i.e. high ethylene content and low saponification degree) was suggested.
For example, JP S63-230757A (patent document 1) suggests a resin composition comprising two EVOH resins having a different ethylene content and saponification degree from each other. The patent document 1 discloses a resin composition employing two EVOH resins so that difference of ethylene content between the EVOH resins is 4 mol % or more, difference of saponification degree between them is 3 mol % or more, and difference of solubility degree parameter between them exceeds a predetermined value. Also, the patent document 1 discloses a multilayered sheet or film including the resin composition as an intermediate layer between polystyrene layers. The multilayered sheet or film may be molded by vacuum-pressure forming to produce a transparent molded article excellent in gas-barrier property and appearance without non-uniformity thickness nor fracture.
JP H8-311276A (patent document 2) discloses an EVOH resin composition comprising two EVOH resins each having an ethylene content different by from 3 to 20 mol %, and boron in a specific concentration. The patent document 2 discloses that a multilayered sheet or film including a layer of the EVOH resin composition as an intermediate layer between polypropylene layers through an adhesive resin layer did not allow to become whitening or uneven stretched causing streak formation when the multilayered sheet or film was heated and drawn with 4 times in the machine direction and 6 times in the transverse direction.